Seismic wave propagation and application of seismic observations in modeling and imaging the structure and dynamics of the Earth's interior: determination of the inner core rotation, mapping the fine structures of the inner core anisotropy, the inner core-fluid core boundary, and lateral variation of core-mantle boundary; the structure of crust and upper mantle in China and east Asia and the tectonics of the region. Approaches include waveform modeling and seismic tomography.